package com.lagou.edu.mvcframework.servlet;

import com.lagou.edu.mvcframework.exception.MvcException;
import com.lagou.edu.mvcframework.annotations.*;
import com.lagou.edu.mvcframework.pojo.Handler;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.*;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class LgDispatcherServlet extends HttpServlet {

    private Properties properties = new Properties();

    private List<String> classNames = new ArrayList<>(); //缓存扫描到的类的全限定类名

    //ioc容器
    private Map<String, Object> ioc = new HashMap<>();

    //handlerMapping
    //private Map<String, Method> handlerMapping = new HashMap<>(); //存储url和method之间的映射关系
    private List<Handler> handlerMapping = new ArrayList<>();

    @Override
    public void init(ServletConfig config) throws ServletException {
        //1.加载配置文件 springmvc.properties
        String contextConfigLocation = config.getInitParameter("contextConfigLocation");
        doLoadConfig(contextConfigLocation);

        //2.扫描相关的类，扫描注解
        doScan(properties.getProperty("scanPackage"));

        //3.初始化Bean对象（实现ioc容器，基于注解）
        doInstance();

        //4.实现依赖注入
        doAutowired();

        //5.构造一个HandlerMapping处理器映射器，将配置好的url和Method建立映射关系
        initHandlerMapping();

        System.out.println("lagou mvc 初始化完成......");

        //等待请求进入，处理请求
    }

    /**
     * 构造一个HandlerMapping处理器映射器
     * 最关键的环节
     * 目的：将url和method建立关联
     */
    private void initHandlerMapping() {
        if (ioc.isEmpty()) return;

        for (Map.Entry<String, Object> entry : ioc.entrySet()) {
            //获取ioc中当前遍历的对象的class类型
            Class<?> aClass = entry.getValue().getClass();

            if (!aClass.isAnnotationPresent(LagouController.class)) {
                continue;
            }

            String baseUrl = "";
            if (aClass.isAnnotationPresent(LagouRequestMapping.class)) {
                LagouRequestMapping annotation = aClass.getAnnotation(LagouRequestMapping.class);
                baseUrl = annotation.value(); //等同于/demo
            }
            //获取方法
            Method[] methods = aClass.getMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];

                //方法没有标识LagouRequestMapping，就不处理
                if (!method.isAnnotationPresent(LagouRequestMapping.class)) {
                    continue;
                }
                //如果标识LagouRequestMapping，就处理
                LagouRequestMapping annotation = method.getAnnotation(LagouRequestMapping.class);
                String methodUrl = annotation.value(); // /query
                String url = baseUrl + methodUrl; //计算出来的url：/demo/query

                //方法上有没有LagouSecurity，有的话取值
                Set<String> userNameSet = new HashSet<>();
                if (method.isAnnotationPresent(LagouSecurity.class)) {
                    LagouSecurity securityAnnotation = method.getAnnotation(LagouSecurity.class);
                    String[] value = securityAnnotation.value();
                    userNameSet = Set.copyOf(Arrays.asList(value));
                } else {
                    //方法上没有，看类上有没有LagouSecurity，类上有取类上，没有则不校验
                    if (aClass.isAnnotationPresent(LagouSecurity.class)) {
                        LagouSecurity classAnnotation = aClass.getAnnotation(LagouSecurity.class);
                        String[] value = classAnnotation.value();
                        userNameSet = Set.copyOf(Arrays.asList(value));
                    }
                }

                //把method所有信息及url封装为一个Handler
                Handler handler = new Handler(entry.getValue(), method, Pattern.compile(url), userNameSet);

                //计算方法的参数位置信息 HttpServletRequest request, HttpServletResponse response, String name
                Parameter[] parameters = method.getParameters();
                for (int j = 0; j < parameters.length; j++) {
                    Parameter parameter = parameters[j];

                    if (parameter.getType() == HttpServletRequest.class || parameter.getType() == HttpServletResponse.class) {
                        //如果是request和response对象，那么参数名称写HttpServletRequest和HttpServletResponse
                        handler.getParamIndexMapping().put(parameter.getType().getSimpleName(), j);
                    } else {
                        handler.getParamIndexMapping().put(parameter.getName(), j); //<name, 2>
                    }
                }

                //建立url和method之间的映射关系（map缓存起来）
                //handlerMapping.put(url, method);
                handlerMapping.add(handler);
            }
        }
    }

    //实现依赖注入
    private void doAutowired() {
        if (ioc.isEmpty()) return;

        //有对象，再进行依赖注入处理

        //遍历ioc中所有对象,查看对象中的字段，是否有@LagouAutowired注解，如果有，需要维护依赖注入关系
        for (Map.Entry<String, Object> entry : ioc.entrySet()) {
            //获取bean对象中的字段信息
            Field[] declaredFields = entry.getValue().getClass().getDeclaredFields();
            //遍历判断处理
            for (int i = 0; i < declaredFields.length; i++) {
                Field declaredFiled = declaredFields[i]; //@LagouAutowired private IDemoService demoService;
                if (!declaredFiled.isAnnotationPresent(LagouAutowired.class)) {
                    continue;
                }
                //有LagouAutowired注解
                LagouAutowired annotation = declaredFiled.getAnnotation(LagouAutowired.class);
                String beanName = annotation.value(); //需要注入的bean的id
                if ("".equals(beanName.trim())) {
                    //没有配置具体的bean id，那就需要根据当前字段的类型注入（接口注入） IDemoService
                    beanName = declaredFiled.getType().getName();
                }

                //开启赋值
                declaredFiled.setAccessible(true); //强制访问

                try {
                    declaredFiled.set(entry.getValue(), ioc.get(beanName));
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //ioc容器
    //基于classNames缓存的类的全限定类名，以及反射技术，完成对象创建和管理
    private void doInstance() {
        if (classNames.size() == 0) return;
        try {
            for (int i = 0; i < classNames.size(); i++) {
                String className = classNames.get(i);  //com.lagou.demo.controller.DemoController

                //反射
                Class<?> aClass = Class.forName(className);
                //区分controller，区分service
                if (aClass.isAnnotationPresent(LagouController.class)) {
                    //controller的id此处不做过多处理，不取value，就拿类的首字母小写作为id，保存到ioc中
                    String simpleName = aClass.getSimpleName();//DemoController
                    String lowerFirstSimpleName = lowerFirst(simpleName); //demoController
                    Object o = aClass.newInstance();
                    ioc.put(lowerFirstSimpleName, o);
                } else if (aClass.isAnnotationPresent(LagouService.class)) {
                    LagouService annotation = aClass.getAnnotation(LagouService.class);
                    //获取注解value值
                    String beanName = annotation.value();

                    //如果指定了id，就以指定的为准
                    if (!"".equals(beanName.trim())) {
                        ioc.put(beanName, aClass.newInstance());
                    } else {
                        //如果没有指定，就以类名首字母小写
                        beanName = lowerFirst(aClass.getSimpleName());
                        ioc.put(beanName, aClass.newInstance());
                    }

                    //service层往往是有接口的，面向接口开发，此时再以接口名作为id，放入一份对象到ioc中，便于后期根据接口类型注入
                    Class<?>[] interfaces = aClass.getInterfaces();
                    for (int j = 0; j < interfaces.length; j++) {
                        Class<?> anInterface = interfaces[j];
                        //以接口的全限定类名作为id放入
                        ioc.put(anInterface.getName(), aClass.newInstance());
                    }
                } else {
                    continue;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //首字母小写方法
    public String lowerFirst(String str) {
        char[] chars = str.toCharArray();
        if ('A' <= chars[0] && chars[0] <= 'Z') {
            chars[0] += 32;
        }
        return String.valueOf(chars);
    }

    //扫描类
    //scanPackage:com.lagou.demo package->磁盘上的文件夹（File） com/lagou/demo
    private void doScan(String scanPackage) {
        String scanPackagePath = Thread.currentThread().getContextClassLoader().getResource("").getPath() + scanPackage.replaceAll("\\.", "/");
        File pack = new File(scanPackagePath);

        File[] files = pack.listFiles();

        for (File file : files) {
            if (file.isDirectory()) { //子package
                //递归
                doScan(scanPackage + "." + file.getName()); //com.lagou.demo.controller
            } else if (file.getName().endsWith(".class")) {
                String className = scanPackage + "." + file.getName().replaceAll(".class", "");
                classNames.add(className);
            }
        }
    }

    //加载配置文件
    private void doLoadConfig(String contextConfigLocation) {
        InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);
        try {
            properties.load(resourceAsStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //处理请求：根据url找到method对应的方法，进行调用
        //获取url
        //String requestURI = req.getRequestURI();
        //Method method = handlerMapping.get(requestURI); //获取到一个反射的方法
        //反射调用，需要传入对象，参数，此处无法完成调用，没有把对象缓存起来，也没有参数！改造initHandlerMapping()
        //method.invoke()

        //根据uri获取到能够处理当前请求的handler（从handlerMapping中（list））
        //Handler handler = getHandler(req);
        Handler handler = null;
        try {
            handler = getHandler(req);
            resp.getWriter().write("access is success!");
        } catch (MvcException e) {
            resp.getWriter().write(e.getMessage());
            return;
        }

        if (handler == null) {
            resp.getWriter().write("404 not found");
            return;
        }

        //参数绑定
        //获取所有参数类型数组，这个数组的长度就是我们最后要传入的args数组的长度
        Class<?>[] parameterTypes = handler.getMethod().getParameterTypes();

        //根据上述数组长度，创建一个新的数组（参数数组，是要传入反射调用的）
        Object[] paraValues = new Object[parameterTypes.length];

        //以下就是为了向参数数组中塞值，而且还得保证参数的顺序和方法中形参顺序一致
        Map<String, String[]> parameterMap = req.getParameterMap();

        //遍历request中所有参数（填充除了request，response之外的所有参数）
        for (Map.Entry<String, String[]> param : parameterMap.entrySet()) {
            //name=1&name=2 name[1,2]
            String value = StringUtils.join(param.getValue(), ","); //如同1，2

            //如果参数和方法中的参数匹配上了，填充数据
            if (!handler.getParamIndexMapping().containsKey(param.getKey())) {
                continue;
            }

            //方法形参确实有该参数，找到它的索引位置，对应的把参数值放入paraValues
            Integer index = handler.getParamIndexMapping().get(param.getKey()); //name在第2个位置
            paraValues[index] = value; //把前台传递过来的参数值填充到对应的位置去
        }

        int requestIndex = handler.getParamIndexMapping().get(HttpServletRequest.class.getSimpleName()); //0
        paraValues[requestIndex] = req;

        int responseIndex = handler.getParamIndexMapping().get(HttpServletResponse.class.getSimpleName()); //1
        paraValues[responseIndex] = resp;

        //最终调用handler的method属性
        try {
            handler.getMethod().invoke(handler.getController(), paraValues);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    private Handler getHandler(HttpServletRequest req) throws MvcException {
        if (handlerMapping.isEmpty()) {
            return null;
        }
        String url = req.getRequestURI();

        for (Handler handler : handlerMapping) {
            Matcher matcher = handler.getPattern().matcher(url);
            if (!matcher.matches()) {
                continue;
            }
            //找到合适的handler后需校验权限
            checkSecurity(handler, req.getQueryString());
            return handler;
        }
        return null;
    }

    private void checkSecurity(Handler handler, String paramStr) throws MvcException {
        if (handler == null) return;
        //获取有权限处理的userName
        Set<String> userNameSet = handler.getUserNameSet();
        if (userNameSet == null || userNameSet.isEmpty()) {
            throw new MvcException("access is no permission");
        }
        if (StringUtils.isBlank(paramStr)) {
            throw new MvcException("access is no permission");
        }

        String[] paramArrays = paramStr.split("&");
        for (String paramArray : paramArrays) {
            String[] param = paramArray.split("=");
            if ("name".equalsIgnoreCase(param[0])) {
                if (!userNameSet.contains(param[1])) {
                    throw new MvcException("access is no permission");
                }
            }
        }
    }
}
